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In recent years, digital pre-distortion has emerged as a powerful approach to compensate linear and non-linear imperfections of the transmitter. Previous solutions are either based on factory calibration or use a local auxiliary receiver. Here, we present a digital pre-distortion architecture to compensate transmitter frequency response and I/Q skew, which relies upon a feedback from the far-end receiver and uses the signal propagated over the optical link. The effectiveness of the proposed solution is validated over different transmission systems for dual-polarization 64 QAM net 400 Gb/s and 16 QAM net 200 Gb/s signals.

To guarantee nonnegative signals in optical wireless communication systems, flipped orthogonal frequency division multiplexing (Flip-OFDM) transmits the positive and negative parts of the signal over two consecutive OFDM subframes (positive subframe and negative subfame, respectively). The conventional receiver for Flip-OFDM recovers the data by subtracting the negative subframe from the positive one. However, the signal analysis shows that the signals in the two subframes contain the information of the transmitted data and can be used together to decode the data. An iterative receiver is then proposed to improve the transmission performance of Flip-OFDM by exploiting the signals in both subframes. Simulation results show that the proposed iterative receiver provides significant signal-to-noise ratio gain over the conventional receiver. Moreover, the iterative receiver also outperforms the existing advanced receiver.

We demonstrate analytically a novel scheme to obtain polarization-independent operation in low-cost coherent OOK receivers, suitable for access networks. We move from a well-known phase-diversity receiver, exploiting a 3 × 3 coupler, three photodiodes, and basic analogue processing. If that receiver is modified to inject the local oscillator (or the signal) into two inputs with proper polarization states, we show, by both mathematical derivation and numerical simulations, that the resulting electrical signal can be polarization-independent; this is attained only if the frequency-detuning between the signal carrier and the local oscillator is high enough, so that intrinsic second order distortions can be spectrally isolated and suppressed by the low-pass filtering of the receiver.

We propose and demonstrate a dual-detector optical receiver for directly modulated reflective semiconductor optical amplifier (RSOA)-based transmitters employing a delay interferometer as an optical equalizer at the receiver. We show through experiment that the dual-detector receiver not only improves the receiver sensitivity but also lowers the error floor by widening the eye opening at the receiver. We also demonstrate upstream transmission of a 10-Gb/s RSOA signal over a 40-km single-fiber loopback configured network.

Recently, coherent polarization-multiplexed quadrature-phase-shift keying has attracted considerable interest. Enabled by progress in ultrafast digital signal processing electronics, it can carry 4 bits per symbol and has been proposed for 100-Gb/s transmission at a reduced 25-GBaud line rate. Several different receiver structures are possible, whose performance, complexity, and design issues are varied. In this letter, we concentrate on a receiver employing single-ended, rather than balanced, detection. We analyzed its performance and found that, by properly tailoring its design parameters, the single-ended receiver may closely approach the performance of the more expensive balanced receiver, over a practically relevant received-signal dynamic range.

We propose and experimentally demonstrate a novel communication system scheme with an optical injection-locked vertical-cavity surface-emitting laser (OIL-VCSEL) acting both as a transmitter and as a receiver, under an identical forward-bias condition. We show that an OIL-VCSEL can function as a receiver with a small signal modulation bandwidth of ~20 GHz, and for large signal digital modulation with data rate as high as 12 Gb/s.

A dc photocurrent rejection technique for optically differential receivers is proposed to reduce the sensitivity of receiver latency to variations in average input photocurrent. This is particularly attractive in optoelectronic very large scale integration applications, where array-scale nonuniformity is significant. Using optically enabled ring oscillator experiments, we demonstrate that the technique is capable of removing between 50%-75% of the skew in large synchronously operated arrays of common-gate amplifier- and transimpedance amplifier-based optical receivers.

For the first time a two-chip wavelength-selective InGaAs-InP Fabry-Perot p-i-n receiver for dense wavelength-division-multiplexed systems is presented. This concept allows one to easily place the p-i-n diode outside the resonant cavity. A cavity length of more than 30 /spl mu/m is applied to obtain a small optical bandwidth of the receiver. The device can be combined with micromachined actuators for wavelength tuning. First measurements of the receiver showed a full-width at half-maximum bandwidth of 0.6 nm and a finesse of 53. The overall losses of the receiver including fiber-to-chip coupling losses are 6.6 dB.

We calculated the effect of the transmitter speed and receiver bandwidth on the electrical eye margin performance of a 10-Gb/s NRZ optical fiber transmission system. The transmitter under consideration used a 1.5 /spl mu/m DFB-laser externally modulated by a zero-chirp LiNbO/sub 3/ modulator with NRZ, 2/sup 7/-1 PRBS data. The receiver was a pin-diode based direct detection receiver. Main results are (1) near optimum system performance is achieved when the 10-90% rise/fall-time of the transmitter output is 40 ps, only small improvement is obtained by using faster speeds and, (2) the optimum bandwidth of the receiver is at 10 GHz (the baudrate) for both the back-to-back and the 120-km transmission configuration. Thus, the optimum receiver bandwidth is at the baudrate (10 GHz) which is in conflict with accepted practice which suggests approximately 0.6/spl times/ baudrate (6 GHz). The reason for this discrepancy is that we considered an optically amplified NRZ transmission system where the optical power level at the receiver input is well above the receiver sensitivity. Therefore, the impact of thermal noise is negligible and the system is dominated by ISI, which can be reduced by increasing the receiver bandwidth.

In this paper, we will report the performance of a high-sensitivity (-28.7 dB) avalanche photodiode (APD) receiver, constructed with a low-noise superlattice APD, for l0-Gb/s applications. This receiver sensitivity value is only about 4-5 dB away from that of a commercially realizable optical pre-amplifier receiver at this bit-rate. Using this receiver and a transmitter with an output optical power of only -4 dB, we are able to transmit data over 61 km of standard fiber, including system operational margins, without using any optical amplifiers.

High data rate communications are of interest for many applications. In fiber-based broadcast systems, high receiver sensitivity and high transmitter power translate into the ability to reach more customers. For space applications, high receiver sensitivity and high optical power are essential since it is impossible to use amplifiers between the transmitter and receiver. We describe here the experimental demonstration of a 10-Gbps communications system with a receiver sensitivity of 77 photons/bit at a bit error rate of 10/sup -9/ and a one-watt optical transmitter based on an erbium-doped fiber amplifier pumped by tapered-gain-region semiconductor lasers. >

The authors report a novel differential, integrated optical receiver capable of generating symmetric, complementary data signals at the preamplifier stage. The receiver offers superior bandwidth and common mode noise rejection over the conventional transimpedance receiver. A wide-bandwidth receiver implementation in which an InGaAs p-i-n photodiode is DC coupled between a pair of current-source circuits embedded in a GaAs/AlGaAs HBT preamplifier IC is demonstrated. >

A novel optical homodyne receiver for binary PSK optical communication systems that can break the receiver sensitivity limit determined from the shot noise is proposed. The receiver consists of the optical preamplifier, the feedforward circuit to reduce the signal-spontaneous beat noise, and the conventional double-balanced homodyne receiver. The operation principle of the receiver and the analysis of the sensitivity are described. >

A novel, electronically integrated, four-channel optical receiver is demonstrated which is designed for electronic channel selection of different wavelength channels in a wavelength-division-multiplexing-based optical network. The receiver consists of four InAlAs-InGaAs metal-semiconductor-metal (MSM) photodetectors that can be independently switched on or off electronically by a digital signal. An optical extinction ratio of 20 dB for the MSM detector was observed. The sensitivity of this optoelectronic integrated circuit receiver is -25.2 dBm at 1.2 Gb/s data rate. >

The use of semiconductor diode lasers simultaneously as heterodyne receivers and lightwave transmitters in a full-duplex single optical fiber transmission system is reported. A transmission distance of 16 km, limited by Rayleigh backscattering, is obtained at a bit rate of 40 Mb/s for this simple system, which requires no optical couplers or photodiodes. The proposed operation is analogous to that of the so-called autodyne radio receiver in which the local oscillator circuit also performs the heterodyne mixing. The optical counterpart is called a self-heterodyne mixer and offers the same frequency selectivity and tunability as a conventional heterodyne detector but with reduced receiver complexity. In the self-heterodyne receiver, an optical signal to be detected is introduced directly into the lasing cavity by coupling the signal into the laser through an uncoated cleaved end facet. Changes in the optical cavity field, which result from interference between the lasing mode and the injected signal, modulate the rate of stimulated carrier recombination and thus produce a change in the injection current. This alternating current component is detected and amplified in the laser active region bias. >